DE 10 2011 077 552 A1 discloses a hydraulic configuration for a transmission, by which the supply of a hydraulic medium of components of a vehicle's transmission can be carried out. The hydraulic configuration includes at least one main pump device driven on the drive side for supplying a primary hydraulic circuit with a primary pressure, and is additionally designed with at least one auxiliary pump that can be driven on the output side, which is provided for supplying a secondary hydraulic circuit with a secondary pressure. The auxiliary pump device is connected either directly to the primary hydraulic circuit or directly to the secondary hydraulic circuit, whereas a coupling device is provided for coupling the auxiliary pump device to the output of the transmission or a switching-on device for opening the hydraulic medium supply of the auxiliary pump device coupled with the output. In the case of a main pump device that is not driven, the coupling device or the switching-on device can be controlled as a function of a supply pressure in the primary hydraulic circuit and/or as a function of a lubrication pressure in the secondary hydraulic circuit.
As a function of the direct connection between the auxiliary pump device and the primary pressure circuit or the secondary pressure circuit, either the secondary pressure circuit or the primary pressure circuit cannot be supplied with hydraulic fluid by the auxiliary pump device below a pressure level of the primary pressure defined by the spring pressure device acting on the system pressure valve, by which under-supply states in the area of the primary pressure circuit or in the area of the secondary pressure circuit cannot be prevented by the auxiliary pump device.
A control device for an automated toothed wheel change-gear transmission is described in DE 10 2009 005 756 A1. The control device or the hydraulic control features a main pump, which is driven by a drive unit of a motor vehicle. In addition to the main pump, the hydraulic control unit features an auxiliary pump, which is characterized by high manufacturing costs and is driven by an electric motor. The electric motor is controlled by the electronic control unit. Thus, the operation of the auxiliary pump is independent of the operating state of the drive unit of the motor vehicle. The auxiliary pump sucks in oil by a suction filter and, at appropriate pressure conditions, delivers it to the high-pressure system or a primary pressure circuit by a non-return valve. Thereby, the non-return valve is arranged in such a manner that an oil flow is blocked starting from the primary pressure circuit in the direction of the auxiliary pump. By the non-return valve, the auxiliary pump is connected to a third connection of a working pressure slide and thus also to a return line to the working pressure slide. The auxiliary pump may also convey oil into a lubrication/cooling system by the working pressure slide and assist the main pump in the oil supply of the hydraulic control system, by which the main pump may be designed to be smaller. The auxiliary pump may, in particular, also ensure the oil supply if the drive unit of the motor vehicle and thus the main pump are out of operation. Thus, a so-called “start-stop operation” of the motor vehicle is enabled.
However, the supply of a cooling system of a gear set of the toothed wheel change-gear transmission, designed as a dual-clutch transmission, starting from the auxiliary pump then to be driven by the allocated electric motor, can only be realized by a corresponding actuation of the control, which is why short-term under-supply states in the area of the cooling circuit of the gear set cannot be compensated by the auxiliary pump with the desired spontaneity.